Welding method of carbon steel pipe
In the friction welding method, the abutted carbon steel pipes are relatively rotated or slid while pressure is being applied. Then, thus-generated fictional heat is used to soften and weld the ends of the carbon steel pipes to each other. The foregoing method is able to realize advantages in that any skill is not required, the joining operation can be completed in a short time and excessive influence of the operation environment can substantially be eliminated. However, the foregoing method cannot prevent flash of the inner and outer surfaces of the joined portion of the carbon steel pipes. Therefore, there arises a problem in that removal of the flash, in particular, removal of the flash formed on the inner surface requires a long time. As a method to solve the foregoing problem, a radial friction welding method has been developed. In the method, a ring having a wedge-like cross section is inserted between the end surfaces of a pair of carbon steel pipes while securing the pair of the carbon steel pipes, the ring is inwards pushed toward the center of the carbon steel pipe to perform pressure-welding. The pressure-welded joint attains only poor characteristic. Therefore, there is no report about the employment of the method to join the oil-well pipes.
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